This invention deals generally with hoisting slings, and more specifically with a wire rope roundsling with a cover and a window in the cover to facilitate inspection of the wire rope core.
Loop type wire rope roundslings are commonly used to hang items from support structures. One typical use for such slings is to hang trusses which hold lights and special effect devices from girders above a stage. Essentially, roundslings are continuous wire rope loops forming a load bearing core which is enclosed within a cover. Typically, these covers, which are intended to afford protection against the environment and abrasion, are constructed of synthetic fabric and form a complete enclosure around the wire rope core. However, such fabric covers also present a problem.
A major safety requirement for the use of wire rope hoisting devices is that they be inspected before each use, but opaque fabric covers prevent simple visual inspection. The only method presently being used to inspect such roundslings is by touch. That is, the inspector feels the wire rope through the cover attempting to determine if a broken strand can be felt. Such an inspection technique requires highly trained inspectors, and even then it does not have a high confidence level. In addition inspection for corrosion of the wires can not be currently done. It would be very beneficial to have a device which permitted visual inspection of round slings and could therefore provide a high degree of confidence in the results of the inspection.
The present invention provides a simple solution to the problem. A portion of the cover is cut away to provide a window to view the wire rope core. For the present invention, the window is formed near the junction of the ends of the tubular cover by cutting off about a one inch length of part of the circumference of the finished tube. Thus, when the balance of the end of the fabric is attached to the other end of the tube cover, part of the cover is missing and the wire rope core is visible through the location of the missing section of cover. The ends of the tubular cover are joined by heavy stitching in the region of the junction.
To protect the core in the region of the window, a window cover is added there. The window cover typically is a piece of reinforced plastic fabric overlapping and approximately centered on the window, but sewn onto the portion of the cover which remains after the window area is removed. The window cover is large enough to wrap around both the wire rope core and the fabric cover of the round sling at the location of the window, and to have its own ends meet and be attached to each other. In the preferred embodiment the ends of the window cover are attached to each other by the use of Velcro fastening tape.
The method of using the inspection window is not sophisticated, but it works very well. Since the cover covers the wire rope core relatively loosely and is not attached to the core in any way, the fabric cover and the window can be worked around the wire rope core by repeatedly compressing the length of the cover between two hands and then holding one hand tightly on the core and stretching the cover. The motion is essentially the same as when pushing any fabric tube over a long object, except in this case the long object is actually a closed loop. All that is required for the safety inspection is that the wire rope core be viewed as the window passes along it.
The present invention thereby provides a simple and economical means for inspecting the core of a covered roundsling.